In inkjet printers, ink lines are provided to supply ink from an ink reservoir to a printhead. Commonly, there are multiple ink lines (e.g. in a CYMKK printer, there are 5 ink lines connected to the printhead).
It is sometimes necessary for the printhead to be decoupled from the ink lines to enable, for example, replacement of a depleted printhead. Inkjet printers that can prime and deprime the printhead, and purge air bubbles from the printhead, offer the user distinct advantages. For example, removing a depleted printhead can cause inadvertant spillage of residual ink if it has not first been de-primed prior to decoupling. Further, air bubbles trapped in printheads are a perennial problem in inkjet printers, and there is a need for a means to purge such air bubbles from printheads whenever they are present.
It is known in the prior art to provide a pinch valve for the purpose of enabling priming and depriming of the printhead, and for purging of air bubbles from the printhead. In operation, the pinch valve is located directly upstream of the printhead and the pinch valve selectively controls (i) the flow of ink to the printhead, or (ii) the flow of air to the printhead, such that the printhead can be primed or de-primed, or such that an air bubble can be purged from the printhead.
The closest prior art presently known to the applicant is International Publication WO 2011/143698 (published 24 Nov. 2011), which is herein incorporated by reference. In particular, FIGS. 23-27 of WO 2011/143698 teach a pinch valve which selectively controls the flow of ink or air to the printhead for the purposes discussed above.
The operation of this prior art pinch valve is described, for example, at page 39 through to page 48 of WO 2011/143698. The pinch valve is a 2-way (i.e. ink or air), multi-channel (i.e. CYMKK) valve which selectively directs either ink or air to the printhead. In the illustrated embodiment, there are 5 ink lines and 5 air lines which are selectively opened and closed by the operation of the pinch valve.
The ink lines and air lines pass through the pinch valve and the sections of the lines which pass through the pinch valve are formed of a resilient, plastics tubing which, in a default state of the pinch valve, are pinched closed. The resilient tubing is selectively allowed to open to allow the passage of ink or air through the valve to the printhead.
In the prior art pinch valve, the pinching function is performed by a pair of spring-biased, elongate pinch elements which reciprocate linearly along orthogonal paths. The reciprocation of the elongate pinch elements is controlled by cams which are mounted on a rotatable camshaft which, in turn, is controlled by a motor. The elongate pinch elements are biased to a closed (i.e. pinched) position by springs, and are selectively moved to an open (i.e. unpinched) position by the operation of the motor and cam mechanism.